The main objective of this experiment will be to evaluate the effectiveness of a collagen-calcium phosphate gel to induce revitalization of pulpless teeth. Evaluation will include histological examination of excised block sections containing bone and teeth, radiographs and antibody tests of blood samples. SPECIFIC AIMS: 1. To determine the nature of tissue ingrowth into biomechanically debrided teeth which have been filled with collagen-calcium, phosphate gel. a. Vital open apex teeth; b. Non-vital open apex teeth; c. Vital mature teeth; d. Non-vital mature teeth. METHOD: The canals of various maxillary and mandibular incisor teeth of juvenile and adult Rhesus monkeys corresponding to the above conditions will be biomechanically debrided. Cultures will be taken and the canals filled with the gel material when one negative bacterial culture is obtained. Radiographs of all teeth will be taken. Blood samples will be drawn at various time-intervals to test for antibody formation to the collagen gel. Animals will be sacrificed at 6 months and block sections of bone containing teeth will be excised and decalcified. Serial sections will be prepared alternately with Hematoxylin-eosin and Mallory's trichrome stains for histological examination.